Posted on Tuesday, the photo shows what appears to be two brothers in their thirties holding on to each other on a train in Singapore. One of them has down syndrome and according to Kwan seems to be the older brother.

Recounting how he came to take the photo, Kwan said that around 5pm on Tuesday afternoon, he noticed the two men board the train at Outram Park station. The train that was headed towards Pasir Ris on the East-West line jerked and the older brother nearly fell over, but the younger brother hugged him close to keep him from falling.

The two then smiled at each other while what looked like the older brother lay his head on the other's chest to show his heartfelt appreciation.

Kwan was touched by the love between the two, prompting him to post the picture as a reminder to all of the love between siblings.

He said in his post, "Just by looking at their expressions, even without any words said, a bystander can see how much they love each other."

The post has since garnered more than 33,000 likes and 1,500 shares.

When asked how he felt about the overwhelming response to his post, the entrepreneur told Yahoo! Singapore in an email interview, "Usually my posts get an average of 30 likes, so to get 33,000 likes was indeed a shocking experience!"

Kwan, who co-founded travelling music school TravelClef, also said that he has been reading the "heartwarming" Facebook shares of his post as many posted on their siblings' walls to express their love.

"Regardless of the many quarrels and bullying, all siblings will, without a doubt, protect their siblings at all costs," he said. "I do hope that Singaporeans can express their love for their family more often, even if it is through social media sites where they can still hide their shyness behind the veil of the computer screen."